1. Field of the Invention
The present invention relates to a mobility control apparatus, a mobile communication terminal and a mobile communication system.
2. Description of the Related Art
Conventionally, a mobile communication terminal includes a function of mobility control, which performs processing of a position registration request to a mobile communication network and the like, in accordance with the movement of the mobile communication terminal. Moreover, a mobility control apparatus installed in the mobile communication network accommodating the mobile communication terminal therein also includes a function of mobility control. Specifically, the mobility control performs processing such as position registration of the mobile communication terminal, handover and the like, in accordance with the movement of the mobile communication terminal. As shown in FIG. 1, a mobile communication terminal 290 includes a mobility control unit 290a responsible for the function of mobility control. A mobile communication network 230 also includes a mobility control unit 230a responsible for the function of mobility control in a mobility control apparatus and the like.
However, in the conventional mobile communication terminal 290 and the mobile communication network 230, in order to advance the mobility control function of the mobility control units 290a and 230a, such as improving the efficiency of the processing performed by the mobility control unit 290a and the mobility control unit 230a of the mobility control apparatus, the entire mobility control units 290a and 230a need to be re-developed and re-constructed. In other words, as shown in FIG. 1, advanced mobility control units 390a and 330a need to be developed, in which the mobility control function of the mobility control units 290a and 230a is advanced as a whole, and the entire mobility control units 290a and 230a need to be replaced by the entire advanced mobility control units 390a and 330a. 
Therefore, advancement of the mobility control function of the mobile communication terminal or the mobility control apparatus installed in the mobile communication network brought about problems of enormous costs, work and time being required for development as well as replacement of the conventional mobility control unit and the advanced mobility control unit and costs thereof. These problems have prevented the mobility control function of the mobile communication terminal or the mobility control apparatus installed in the mobile communication network from being advanced, and an advanced mobility control method from being introduced into the mobile communication terminal or the mobility control apparatus.